The state of the art includes the following known solutions.
European publication document No. EP2502819 A1 and European patent document No. EP 1878650 B1 describes a product called Vivax Assist. The auxiliary engine is not visible and is mounted in a top-down direction by the seat. The engine is mounted into the seat tube in a top-down direction and is fit for being installed in various frames. Similarly to the present invention, the engine supports treadling after pressing a button on the handlebar. The performance of the approximately 1.8 kg heavy device is 200 Watt. The disadvantages of the engine include that the engine keeps the pedals running in case of, for example, an accident, and that the engine might even break the axis if it cannot keep turning due to stuck pedals. Another disadvantage is that the pinion is always rotated, when the engine is not running, thereby being subject to amortization and providing resistance.
Other known solutions include auxiliary motors mounted into the lower, tilted frame tube. Not all existing frames are fit for being used with such solutions, and the bicycles are also heavier than optimal. A significant disadvantage is that such electric bicycles can be purchased and used only as pre-fitted units and they are unfit for being mounted individually and using unique settings.
European patent document No. EP 1193171 B1 and international patent documents No. WO2005009831 A2 and WO2011146851 A1 describe electric bicycles with auxiliary engine. European patent document No. EP2228293 A2 describes an engine for easy bicycles that drives the axis of the bicycle.
International publication document No. WO2011021164 A2 describes devices for electric bicycles. The emphasis is placed by this invention onto the technical details of the wheel.
International publication document No. WO2013067565 A1 describes a more traditional Pedelec electric bicycle, which is heavier and is fitted with an external auxiliary engine.
A common disadvantage of solutions belonging to the state of art is that they are significantly heavier than 15 to 20 kg, so they are not suitable for sport activities or heavy usage. Another disadvantage is that the user needs to keep the device switched on when riding uphill. Yet another disadvantage is that the design of such devices may cause the back wheel spin freely on wet road, thereby possibly putting the user in danger.